1. Field of the Invention
The present invention relates to a communication system, and more particularly to a method for transmitting data in a multi-user Multiple-Input Multiple-Output (MIMO) communication system.
2. Description of the Related Art
A MIMO system is one of the important technologies used to achieve a high rate and a high reliability of data transfer in wireless channels. In the case where a feedback channel is used, a transmitter can use channel information as part of the feedback. In an actual system, determined feedback channel capacity is permitted. Therefore, in the multi-user channel environment, a method for designing a transmitter partially uses channel knowledge. Recently, research into a multi-user diversity has been actively conducted in order to output a large quantity of data under a multi-user communication environment in which a packet is transmitted to a user terminal having the highest Signal-to-Noise Ratio (SNR). The conventional research for the multi-user diversity may insufficiently use user diversity in the case where transmission antennas are allocated to different users. Therefore, in a multi-user MIMO system, determined feedback information and user diversity are simultaneously considered in order to design a transmission preprocessing technology, i.e. a transmission preceding.
Further, since the capacity of the feedback channel is limited, it is necessary to restrict an uplink transmission ratio for each user. In order to simultaneously support a downlink transmission for a single user and multiple users in the MIMO system, more feedback information is transmitted from a receiver to a transmitter. Thus, there is a problem in that feedback overhead increases.